<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        .one{
            width: 1000px;
            height: 1000px;
            background-color: #18bebe;
        }
        .two{
            width: 100px;
            height: 100px;
            background-color: red;
            position: absolute;
            z-index: 4;


        }
        .three{
            width: 100px;
            height: 100px;
            background-color: #555555;
            position: absolute;
            z-index: 3;
        }

    </style>

</head>
<body>
<div class="one">
    <div class="two"></div>
    <div class="three"></div>
</div>
</body>
</html>